Add support for "dependencies" in pg_restore_extended_stats()

Add support for "dependencies" in pg_restore_extended_stats()

This commit adds support for the restore of extended statistics of the
kind "dependencies", for the following input data:
[{"attributes": [2], "dependency": 3, "degree": 1.000000},
 {"attributes": [3], "dependency": 2, "degree": 1.000000}]

This relies on the existing routines of "dependencies" to cross-check
the input data with the definition of the extended statistics objects
for the attribute numbers.  An input argument of type "pg_dependencies"
is required for this new option.

Thanks to the work done in 0e80f3f88dea for the restore function and
e1405aa5e3ac for the input handling of data type pg_dependencies, this
addition is straight-forward.  This will be used so as it is possible to
transfer these statistics across dumps and upgrades, removing the need
for a post-operation ANALYZE for these kinds of statistics.

Author: Corey Huinker <corey.huinker@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/CADkLM=dpz3KFnqP-dgJ-zvRvtjsa8UZv8wDAQdqho=qN3kX0Zg@mail.gmail.com